exports.getPostData=function(ctx){
  return new Promise((resolve, reject) => {
    try {
      let str='';
      ctx.req.on('data',(chunk)=>{
        str+=chunk;
      });
      ctx.req.on('end',(chunk)=>{
        resolve(str)
      })
    }catch (e) {
      reject(e)
    }
  });
};
